1. Field of the Invention
This invention relates to a substrate treating method and substrate treating apparatus for removing organic substances from substrates. In particular, the invention relates to a substrate treating method and substrate treating apparatus for removing a reaction product, which is an organic substance, from substrates. More particularly, the invention relates to a substrate treating method and substrate treating apparatus for removing, by using a removal liquid, a reaction product generated on surfaces of substrates having a patterned film formed by dry etching using a resist film as a mask.
2. Description of the Related Art
In manufacture of semiconductor devices, an etching process is carried out to make a pattern, by using a resist film as a mask, from a film of metal such as aluminum, copper or the like formed on the surface of a substrate, e.g. semiconductor wafer. For forming a microcircuit pattern in the etching process, dry etching such as RIE (Reactive Ion Etching) is employed.
Reactive ions used in dry etching have such strong power as to resolve the resist film to some extent before the etching of the metal film is completed. Part of the resist film undergoes a change in property, turns into a reaction product such as a polymer, and deposits on side walls of the metal film. This reaction product cannot be removed in a resist removing process to follow. It is therefore necessary to remove the reaction product after the resist removing process.
Conventionally, therefore, a reaction product removing process is carried out after the dry etching process, to remove the reaction product from the side walls of the metal film by supplying the substrate with a removal liquid capable of removing the reaction product. The above “reaction product resulting from a change in property of the resist” is an organic substance. A process may also be carried out to supply the substrate with an organic substance removal liquid for removing other organic substances from the substrate.
With increasingly fine patterns and changes in preliminary processes of late years, the reaction product now has diverse properties. This poses a problem that the conventional removing process requires a long time for removing the reaction product. As a solution to this problem, a substrate treating apparatus of the single-substrate or piecemeal processing type has been developed to replace a substrate treating apparatus that immerses substrates into a removal liquid. This piecemeal type apparatus removes the reaction product by supplying a removal liquid to the surface of a substrate held and spun by a spin chuck inside a scatter preventive cup. The piecemeal type substrate treating apparatus has advantages of improved displacement efficiency of the removal liquid and reduced consumption of deionized water and an intermediate rinse solution for cleaning the substrates. As noted above, the reaction product has diverse properties, and the conventional removing process requires a long time for removing the reaction product. The above piecemeal type substrate treating apparatus has been developed to realize improved displacement efficiency of the removal liquid and reduced consumption of deionized water and the intermediate rinse solution.
The removal liquid used in such a substrate treating apparatus requires cost for post-discharge treatment, and a restraint on its usage is desired. However, the conventional substrate treating apparatus is designed without sufficient consideration as to the restraint on usage of such removal liquid.
Further, such a substrate treating apparatus uses a hot removal liquid, and a gas containing chemical components generates from this removal liquid. When an intermediate rinse solution is used, a gas containing chemical components generates also from the intermediate rinse solution. A diffusion of such gases containing chemical components could affect equipment installed outside a substrate treating unit in the substrate treating apparatus, or affect results of substrate treatment by the equipment.
Thus, it is conceivable to prevent the gases containing chemical components from diffusing outside the scatter preventive cup by exhausting the atmosphere from the scatter preventive cup. It has been found, however, that a substrate treating apparatus for removing organic substances as well as the reaction product (hereinafter referred to simply as organic substances) cannot effectively remove the organic substances when the atmosphere in the scatter preventive cup is exhausted in time of substrate treatment.
That is, the removal liquid used for removing the organic substances, as distinct from a liquid developer used for development, characteristically has a small moisture content. Thus, the removal liquid loses some of its capability for removing the organic substances and cannot remove the organic substances effectively when the moisture in the removal liquid vaporizes due to air currents generated by exhaustion of the atmosphere from the scatter preventive cup. The air currents thus generated may ruffle the surface of the removal liquid or oxidize the removal liquid. These phenomena could also be the cause of the ineffective removal of the organic substances.
Such lowering of the capability for removing the organic substances is salient particularly when, after the removal liquid is supplied to the surface of a substrate, the substrate is temporarily stopped spinning, or is spun at such a low speed as to prevent the removal liquid scattering from the substrate, or is spun intermittently.